Magnetoresistive random access memory (MRAM) typically employs an array of magnetic storage elements, or cells, which are each located at, or near, an intersection, or crossing, of a corresponding word line with a corresponding bit line. Those skilled in the art know that spin transfer can be used as an alternative to, or in addition to, an external magnetic field in programming current perpendicular to plane (CPP) configurations MRAM cells, which may be either of the magnetic tunnel junction (MTJ) type or of the spin valve (SV) type. When a spin-polarized write current passes through a data storage layer of the cell, which is a free ferromagnetic layer, a portion of the spin angular momentum of the electrons incident on the data storage layer is transferred to the data storage layer. A spin transfer effect, that is caused by conduction electrons traveling from a pinned ferromagnetic layer of the cell to the data storage layer, switches the magnetization orientation of the data storage layer from a direction that is opposite to that of the magnetization orientation of the pinned layer, to a direction that coincides with that of the magnetization orientation of the pinned layer, for example, to program, or write, a logical “0” to the cell; and, a spin transfer effect that is caused by conduction electrons traveling in the opposite direction, switches the magnetization orientation of the data storage layer back to the direction that is opposite to that of the magnetization orientation of the pinned layer, for example, to write a logical “1” to the cell.
In some MRAM arrays, data storage layers may be susceptible to an inadvertent switching, for example, caused by thermally induced lattice vibration. This thermal instability of the storage layers may be due to a reduction in the size and/or magnetization thereof. Furthermore, a significant amount of Joule heating may be generated by a write current, and those cells, which are adjacent to one being written, particularly in ultra high density MRAM arrays, may be inadvertently switched due to the heating. Thus, there is a need for MRAM cell configurations that provide for enhanced thermal stability.